It is recognized that accidents occurring in industrial environments are often a consequence of carelessness. Simple, low cost precautionary measures can sometimes make a big difference in industrial accident occurrence rate. One such known safety measure consists in providing a locking member having at least a few padlock shackle engaging bore means, wherein the keys for the various padlocks are to be held by a number of different persons. For example, in the case of a fluid line controlled by a valve, having more than one padlock to lock the butterfly valve is desirable, since more than one person would need to authorize such unlocking, and any of these persons could put his veto on the unlocking of the locking device, a desirable safety feature.
One such example of multi-padlock safety lock member is disclosed in U.S. Pat. No. 5,052,939 issued on Oct. 1, 1991 to William KOCH. One drawback of these known safety locks is that, once all the padlocks are disengaged from the safety lock ears, the two arms constituting the safety lock will tend to freely open up, which could undesirably lead to the accidental release of the safety lock from the control box. It is understood that with these safety locks, the idea is not really to deter a person having a criminal intention, but more so to prevent accidents provoked mainly by carelessness.
In U.S. Pat. No. 5,165,263 issued 24 Nov. 1992 to Claude PERRON and to the present inventor, there is disclosed a locking device for locking a single control lever of the valve mounted transversely of a fluid line. This two part locking device includes a male member and a female member. The male member includes a U-shape part, engaging the outer wall of the fluid line, and a transverse channel part, extending away from the fluid line and engaging the valve handle and having a flange with a number of lengthwisely spaced bores. The female member includes a casing, with a through passage sized for through engagement by the channel part, and with a transverse pocket extension with a number of lengthwisely spaced bores, the female member extension forming a lateral pocket for through engagement by the channel part flange. More than one padlock interlock selected pairs of bores from the male member flange and from the female member pocket, to provide multiple interlock between two parts of the lock device, so as to prevent unauthorized actuation of the valve control lever.
Valve assemblies that control fluid flow in a fluid conduit may be of various designs. Usually, each such valve assembly includes at least the three following elements:
(a) a valve flap, located inside the fluid conduit and having a shape complementary to that of the internal diameter of the fluid conduit, so that, upon extending transversely of the fluid conduit, fluid flow is completely stopped;
(b) a valve-operating shaft, integrally carried by the valve flap and radially outwardly projecting from the fluid conduit, wherein rotation of the shaft tilts the valve flap between a closed limit condition, transverse to the fluid conduit, and a fully opened limit condition, coaxial to the fluid conduit; the radially outward portion of the shaft being generally shielded by a tubular radial extension, integral to the fluid line; and
(c) an elongated control handle, transversely carried by the radially outer end of the valve-operating shaft.
A butterfly valve is a special type of fluid flow control valve, which includes the two following additional elements:
(a) an elbowed lever, pivoted at its intermediate elbowed section to an intermediate section of the elongated control handle, for pivotal motion about the same plane as the control handle; a coil spring generally biasing the distal end portions of the elbowed lever and control handle, away from one another; and the proximate end of the elbowed lever forming a pointed tip; and
(b) a discoid plate, transversely anchored to the tubular radial shield extension surrounding the valve rotating shaft, and having a notched sector shape portion beneath the control handle, a selected notch being engaged by the pivotal elbowed lever under bias from the coil spring.
In these butterfly valves, the control handle can be pivoted, to tilt the valve flap inside the fluid conduit, only after release of the elbowed lever proximate tip from the discoid plate notch, such lever release occurring by manually grasping the lever distal end portion to draw same toward the control handle distal end portion, against the bias of the coil spring.
None of the existing art of valve locking devices specifically deals with butterfly valves.